Seabed excavation is often performed by dredging, for example to retrieve valuable alluvial placer deposits or to keep waterways navigable. Suction dredging involves positioning a gathering end of a pipe or tube close to the seabed material to be excavated, and using a surface pump to generate a negative differential pressure to draw water and nearby seafloor sediment into and up the pipe. Cutter suction dredging further provides a cutter head at or near the suction inlet to release compacted soils, gravels or even hard rock, to be drawn into the pipe.
A problem with prior art dredging devices is that the suction inlet or pipe can become blocked with large chunks of ‘oversize’ material. One method for preventing oversize material from blocking the pipe is to place a screen over the inlet end of the pipe. However, this typically just transfers the problem to the screen, and oversize material can collect on the screen causing a blockage at the inlet.
Any such blockages are highly undesirable as they reduce efficiency of the operations. At significant water depths, e.g. over 1000 m, they can become particularly problematic as it is not possible to readily perform maintenance or retrieve the device to the surface.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.